KR19980018646A - Evaporation system - Google Patents

Abstract

According to the present invention there is provided a membrane based evaporation permeation system for selectively removing steam from a fluid feed stream, in which a countercurrent sweep flow with a particular partial pressure of steam to be removed is used.

Description

Evaporation system

Evaporation permeation is a membrane based process that can be used to separate the vapor mixture. In one example of such a process, a vapor phase mixture of vapor A and vapor B is fed to the supply side of the membrane, while a vacuum pump or gaseous sweep stream is usually combined with a condenser to provide vapor B to the permeate side of the membrane. Maintain a sufficiently low partial pressure for the to provide a chemical potential gradient for vapor B across the membrane. Primarily steam B and some steam A are transferred to the permeate side of the membrane to form a vapor phase permeate.

The key to the development of a low cost and effective vapor permeation process is the method used to maintain the low partial pressure of steam B on the permeate layer of the membrane. The prior art describes a method of reducing the partial pressure of vapor B on the permeate side of the membrane by applying a vacuum to the permeate side of the membrane to reduce the total pressure of the permeate. However, for many applications, the cost and complexity of the vacuum system has found this to be impractical. Moreover, vacuum drive systems often leak, allowing air to enter the system. For many separation processes, especially compounds that are sensitive to oxygen or compounds with high flammability, the presence of oxygen is undesirable or poses a risk. Thus, other methods are preferred.

U.S. Patent No. 4,978,430 discloses an evaporation permeation process in which a dry inert gas can be used to dehydrate and concentrate a liquid solution containing an organic compound to maintain the permeate at reduced pressure or to reduce partial pressure. Is disclosed.

US Patent No. 5,226,932 discloses a membrane process for drying non-condensable gases such as air, nitrogen, carbon dioxide or ammonia using a low vacuum level and dried countercurrent sweep gas on the permeate side of the membrane. In addition, U. S. Patent No. 5,108, 464, which is shared with the Applicant, indicates that the sweep gas is introduced to the permeate side of the hollow fiber membrane module at the end of the residual liquid, so that it is mixed with the permeate as it passes along the membrane and then fed into the module. A membrane process is disclosed for drying non-condensable gases, such as low molecular weight hydrocarbons or acid gases, using a countercurrent sweep gas exiting a stage.

U.S. Patent No. 5,034,025 discloses maintaining the difference in the partial pressure of water vapor across the membrane and contacting the low pressure and permeate side of the membrane with a dried organic phase condensable sweep gas, preferably incompatible with water in a countercurrent flow mode, By collecting and condensing the sweep gas containing permeated moisture, water vapor such as air, hydrogen dioxide or natural gas is formed, which includes forming a liquid phase condensate of the two phase organic-aqueous phase and then separating the organic and aqueous phases. A membrane process for drying the contained noncondensable gas is disclosed.

As is evident from the foregoing, the prior art has proposed the use of countercurrent gas phase sweep flow on the permeate side of the separation membrane. However, no guideline has been given as to what characteristics these sweep gases should have. It has been found that in order for the use of countercurrent gaseous sweep flow on the permeate side to be realistic, it must have a low concentration or low partial pressure of vapor B on the permeate side of the membrane. Moreover, in order to maintain a high performance, efficient and low cost system, a method of producing gaseous sweeps containing low concentrations of vapor B must be carefully chosen.

The present invention includes an evaporation permeation process for selectively removing a first vapor from a feed stream containing a mixture of vapors, the process comprising:

(a) providing a membrane having a feed liquid and a permeate side,

(b) directing the feed liquid flow to the feed liquid side of the membrane to recover the residual liquid flow depleted of the first vapor from the feed liquid side of the membrane and recovering the first vapor-rich permeate flow from the permeate side of the membrane Wow,

(c) directing a gaseous sweep flow towards the permeate side of the membrane, causing the sweep flow to flow countercurrent to the feed stream flow;

The partial pressure of the first steam in the sweep flow is sufficiently low such that the ratio of the partial pressure of the first steam in the sweep flow to the partial pressure of the first steam in the residual liquid flow is less than 0.9.

One aspect closely related to the present invention is the method used to create the sweep flow. The present invention includes a method wherein the gaseous sweep flow is selected from membrane separation, adsorption and condensation of a gas obtained from a gas produced by evaporation of purified gas and liquefied gas contained in a vessel.

Another aspect closely related to the present invention is the use of a steam removal process for the first vapor-rich permeate flow. The steam removal process is selected from condensation, adsorption and membrane separation. The vapor removal process may also be used to produce a depleted gas phase flow that can be recycled back to the evaporation process and introduced as a sweep gas in step (c).

1 illustrates a basic process for using a membrane to produce a vapor B-rich permeate flow and a vapor B depleted residual flow and using a countercurrent sweep flow to maintain a low partial pressure of vapor B on the permeate side of the membrane. It is shown.

FIG. 2 shows a process similar to that shown in FIG. 1 except that the sweep flow is generated by the unit based on the membrane.

FIG. 3 shows a process similar to the process shown in FIG. 1 except that the sweep flow is created by a hybrid compression / condensation process.

FIG. 4 shows a process similar to the process shown in FIG. 1 except that the sweep flow is produced by the adsorption process.

FIG. 5 shows a process similar to that shown in FIG. 1 except that the sweep flow is obtained from the purified gas contained in the vessel.

FIG. 6 shows a process similar to that shown in FIG. 1, except that the sweep flow is generated by evaporation of the liquefied gas.

FIG. 7 recycles the gas used for the sweep flow by sweeping the gas used for the sweep flow by directing the vapor B-rich permeate flow to a process based on the second membrane, creating a residual liquid flow depleted of steam B used as the sweep flow. A process similar to that shown in FIG. 1 is shown except that a flow is generated, and a supplemental gas flow is used to offset any gas loss from the second membrane.

FIG. 8 shows a sweep flow by recycling the gas used for the sweep flow by directing the vapor B-rich permeate flow to a compression / condensation process, creating a non-condensable flow depleted of steam B used as the sweep flow. Except for this, a process similar to that shown in FIG. 1 is shown.

FIG. 9 shows that a sweep flow is generated by directing a vapor B-rich permeate flow into the adsorption process to produce a flow depleted of steam B used as a sweep flow, thereby recycling the gas used to understand the sweep flow. Except that, a process similar to that shown in FIG. 1 is shown.

FIG. 10 shows a process similar to that shown in FIG. 1, except that the sweep flow is a gas and a vacuum pump is used in the vapor B-rich permeate flow to enhance efficiency.

1 to 10 are schematic diagrams illustrating various embodiments of the present invention.

For the purposes of the present invention, the following definitions of terms are used.

Vapor: A fluid with a gas phase below the critical point and a boiling point greater than -100 ° C.

Sweep: A gaseous fluid, i.e. a vapor phase fluid that is not a liquid at the operating conditions of the process and can be steam as long as it has a low concentration or partial pressure of vapor B.

Permeate enriched with steam B: The partial pressure of steam B inside the permeate flow divided by the sum of the partial pressure of steam B and the partial pressure of steam A in the permeate flow is greater than the same ratio inside the feed stream. Since the permeate also includes a gaseous sweep flow, this term does not necessarily mean that the partial pressure of steam B in the permeate is greater than the partial pressure of steam B in the feed liquid.

For illustrative purposes, it is assumed that the feed liquid flow contains two vapors, steam A and steam B. Moreover, it is assumed that the membrane is more permeable to steam B than to steam A.

In order for the use of the countercurrent sweep flow to be effective in the removal of the steam, the ratio of the partial pressure of the more permeable steam in the sweep to the partial pressure of the more permeable vapor component in the residual liquid is less than 0.9, preferably more than 0.5. It turned out to be small. If this partial pressure is greater than 0.9, the driving force for the transfer of steam from the feed side of the membrane to the permeate / sweep flow is unacceptably low, which, on the one hand, results in a low feed flow rate, which leads to residual liquid flow. To achieve a certain level of purity. However, if the partial pressure ratio of the permeate is less than 0.9, the driving force is high enough that a suitable feed liquid flow rate can be used to obtain an acceptable, high residual liquid purity, thereby providing an effective and low cost system.

The temperature of the feed liquid must be greater than its condensation temperature in a particular atmosphere, on the one hand greater than the ambient temperature, most preferably higher than 40 ° C., while the pressure of the total feed liquid must be greater than atmospheric pressure, preferably 10 atm Should be smaller than

The separation process that can be achieved by the evaporation process of the present invention is most preferably the removal of water vapor from organic vapor, but can also be applied to the removal of volatile compounds from water or separation of organic and inorganic vapor compounds. In general, the membrane used is selected such that trace components of the feed fluid flow are selectively removed by the membrane, but the invention need not be limited thereto.

The capacitive flow of the sweep flow at the sweep inlet port can be adjusted to provide the desired efficiency. Preferably, the capacitive flow of the sweep flow is such that the partial pressure of the more permeable component on the permeate side of the membrane at the residual liquid end of the module is about the value of the value at the feed side of the membrane at the residual liquid end of the module. Sufficient to reduce as low as 90% or less. Thus, the amount of sweep used depends on the operating conditions and the desired concentration of more permeable components inside the residual liquid flow. In general, the volumetric flow of the sweep flow should be at least 0.5% of the volumetric flow of the mixed permeate side mixture. If the desired concentration in the residual liquid flow is very low and the membrane selectivity is high, the capacitive flow of the sweep flow may be 99% or more of the volumetric flow of the mixed permeate side mixture.

The sweep flow used may be any gas or condensable vapor containing a low concentration of vapor to be removed from the feed liquid flow. For example, in applications where inert gas nitrogen is used to cover flammable solvents, nitrogen gas may be used as the sweep flow. Another example of a fluid that can be used as a sweep flow is the inert gases argon and helium, hydrogen, air, steam, carbon dioxide and carbon monoxide.

The vapor phase mixture comprising the feed liquid flow to the membrane selected for the evaporation process comprises a vent flow of the industrial process, a vapor phase overhead from the distillation process, a supernatant in the reflux process, an industrial process Removal or purification of vaporized liquid from, evaporated industrial process flow, chemical process liquids, fine chemicals, pharmaceutical products, flavors and fragrances from natural products, and from various sources, including fermentation processes. It may be, but is not limited thereto.

The vapor containing the vapor phase feed mixture may actually be any compound having sufficient volatility to be present in the vapor phase. In general, these include compounds having a boiling point below about 200 ° C., preferably above room temperature but below 180 ° C., most preferably above 40 ° C. but below 150 ° C. at 1 atmosphere. Examples of compounds that can be removed from the vapor phase feed mixture by the process of the present invention include, but are not limited to, fluorocarbons such as moisture, freon or halon; Chlorinated hydrocarbons such as methylene chloride, trichloroethylene, trichloroethane, carbon tetrachloride and benzene chloride; Non-chlorinated hydrophobic organics such as benzene, toluene, xylene, ethyl benzene, cyclohexane, hexane and octane; Methanol, ethanol, isopropyl alcohol and other alcohols; Acetone, ethyl acetate, methyl ethyl ketone, methyl t-butyl ketone and other ketones; Nitrobenzene; Phenols and cresols; Formic acid, acetic acid and other organic acids; Amines, acetonitriles, including triethylamine and pyridine; Non-chlorinated hydrophilic organics such as dimethyl formamide, dimethylacetamide and N-methylpyrrolidinone; Volatile inorganic compounds such as, but not limited to, ammonia, bromine, iodine, sulfur dioxide and thionyl chloride.

The types of membranes suitable for use in the present invention may be described broadly as separators used for their selective permeable properties, in particular being relatively permeable to one vapor relative to other vapors within the feed fluid flow. And may be described as a separator that is not reactive with the vapor of interest in the sense that it does not contribute or cause any chemical reaction or conversion with the vapor desired to be removed. The membrane can be made entirely of permselective material or from a permselective material that can be supported on a porous membrane, fabric or screen. Examples of permeable materials useful for such separation processes include polyvinyl alcohol, cellulosic materials, chitin and derivatives thereof; Hydrophilic materials including polyurethanes, polyamides, polyamines, poly (acrylic acid), poly (acrylates), poly (vinyl acetate) and polyethers; Natural rubber, nitrile rubber, polystyrene-butadiene copolymer, poly (butadieneacrylonitrile) rubber; Polyurethane; Polyamides; Polyacetylene; Poly (trimethylsilylpropine); Fluoroelastomers; Poly (vinyl chloride); Poly (phosphazene), especially those having organic substituents; Halogenated polymers such as poly (vinylidene fluoride) and poly (tetrafluoroethylene); Hydrophobic materials such as polysiloxane including silicone rubber, but are not limited thereto. Ion exchange membranes may also be used for some applications. Blends, copolymers and crosslinked variants of these materials are also useful. In most cases crosslinking of the polymer is preferred to provide sufficient resistance to swelling or degradation by components of the feed flow.

The membrane can be isotropic or asymmetric. Moreover, the membrane can be a homogeneous or multilayered composite. In most cases, the membrane material is preferably crosslinked to provide sufficient resistance to swelling or degradation by components of the feed flow. The membrane may be prepared by a solvent phase-inversion process, a thermally induced phase transition process, a melt extrusion process or a wet or dry solvent casting process. In the case of multiple composites, the optional layer can be formed by dip coating, painting, spray coating, solution coating or interfacial polymerization.

For multilayer composites, the support layer that provides mechanical strength to the composite (as opposed to the selective permeable layer) should provide as little resistance as possible to the transfer of permeate species through the selective layer as is technically possible. Moreover, the support layer must be chemically and thermally resistant to operate in a hot feed flow containing various chemical components. Suitable materials for the support membrane include polypropylene, polyacrylonitrile, poly (vinylidene fluoride), poly (etherimide), polyimide, polysulfone, poly (ethersulfone), poly (arylsulfone), poly ( Phenylguinozaline) [(poly (phenylquinoxaline)], polybenzimidazole, and organic polymers such as copolymers and blends of these materials, and inorganic materials such as porous glass, carbon, ceramics and metals Does not.

The membrane can be used in the form of a flat sheet or hollow fiber or tube. For flat sheet membranes, the membrane is disposed inside a plate-and-frame module designed to allow countercurrent flow of permeate flow to feed liquid flow. Spirally wound modules are not suitable because they do not allow countercurrent flow. For hollow fibers or tubes, the feed liquid flow may be located outside (shell side) or inside (tube side) of the fiber. In particular, it is preferable that it is a tube side feed liquid hollow fiber membrane module. The material used in the membrane module must have sufficient chemical and thermal resistance to allow long term operation.

Example 1

Using a system having a structure substantially the same as that shown in FIG. 2, a vapor phase containing 4.8 wt% of water dissolved in isopropyl alcohol (IPA) at a pressure of 0.1 bar (gauge pressure) and a temperature of 95 ° C. The feed solution was fed at a rate of 7.8 kg / hr into the tube of the hollow fiber membrane inside the module with an effective membrane area of 2.8 m 2. The inner surface of the hollow fiber was coated with a selective layer of hydrophilic crosslinked polyamide blended with polyvinyl alcohol.

Sweep flow containing dry air with a temperature of 95 ° C. and a dew point of -29 ° C. at 6.9 bar (gauge pressure), and compressed air of 6.9 bar (gauge pressure) to Aqua, Oregon, Bend, Oregon. It was produced by passing through an air dehydration module (ADU) manufactured by AquaAir, Inc. The pressure of this sweep flow is reduced to atmospheric pressure using a throttle valve and introduced to the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, 280 L (STP) at substantially counter flow to the feed flow. It was made to flow at a rate of / min.

Under the above operating conditions, the residual liquid flow has a water partial pressure of 0.00338 bar (absolute pressure), while the sweep flow inlet has a water partial pressure of 0.0005 bar (absolute pressure), so that the inside of the sweep flow to the water partial pressure inside the residual liquid flow The proportion of water partial pressure of was 0.015. This resulted in a residual liquid flow moisture concentration of 0.1 wt%, corresponding to a water removal rate of 97.9%.

Example 2

Using a system having a structure substantially the same as that shown in FIG. 5, a 2.8 m 2 vapor phase feed solution containing 5.9 wt% of water dissolved in IPA at a pressure of 0.05 bar (gauge pressure) and a temperature of 90 ° C. was obtained. The hollow fiber membrane inside the module with an effective membrane area of was fed into the tube at a rate of 4.4 kg / hr. The inner surface of the hollow fiber was coated with a selective layer of crosslinked hydrophilic polymer of Example 1.

Basically, a nitrogen-containing sweep flow from the gas cylinder at atmospheric pressure and 90 ° C. is introduced into the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, so that it is substantially countercurrent to the flow of the feed liquid at 136 L. (STP) / min.

Under these operating conditions, the residual liquid flow has a water partial pressure of 0.00048 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00002 bar (absolute pressure), so that the residual liquid flow has a partial pressure inside the sweep flow relative to the partial pressure of water inside the residual liquid flow. The proportion of water partial pressure was 0.032. This resulted in a residual liquid flow moisture concentration of 0.01 wt%, corresponding to a water removal rate of 99.8%.

Example 3

Using a system having a structure substantially the same as that shown in FIG. 10, a vapor phase feed solution containing 7.6 wt% of water dissolved in IPA at a pressure of 0.3 bar (gauge pressure) and a temperature of 91 ° C. was 2.8 m 2. It was fed at a rate of 8.5 kg / hr into the tube of the hollow fiber membrane inside the module with an effective membrane area of. The inner surface of the hollow fiber was coated with a selective layer of crosslinked hydrophilic polymer of Example 1.

A sweep flow containing dry air having a temperature of 91 ° C. and a pressure of 0.3 bar (absolute pressure) and a dew point of -30 ° C. at 6.9 bar (gauge pressure) was used, and compressed air at 6.9 bar (gauge pressure) was used. Created by passing the same ADU module as used in 1. The sweep flow of dry air produced by this module is introduced into the permeate side of the membrane at an inlet port located near the residual liquid end of the module, so that the flow of 127 L (STP) / min is substantially countercurrent to the feed flow. It was allowed to flow at a speed. A vacuum pump was used to reduce the pressure of the permeate flow to 0.3 bar (absolute pressure).

Under these conditions, the residual liquid flow has a water partial pressure of 0.00203 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00005 bar (absolute pressure), so that the moisture inside the sweep flow to the moisture partial pressure inside the residual fluid flow. The ratio of partial pressure was 0.024. This resulted in a residual liquid flow moisture concentration of 0.1 wt%, corresponding to a water removal rate of 99.2%.

Example 4

Example 3 was repeatedly performed except for the following: A vapor phase feed containing 9.4 wt% of water at a pressure of 0.1 bar (gauge) was fed to the hollow fiber membrane module at a rate of 6.0 kg / hr. The sweep flow was nitrogen flowing at 57 L (STP) / min at 91 ° C. and 0.3 bar (absolute pressure).

Under these conditions, the residual liquid flow has a water partial pressure of 0.00008 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00002 bar (absolute pressure), so that the water partial pressure inside the sweep flow relative to the moisture partial pressure inside the residual liquid flow. The ratio of was 0.2. This resulted in a residual liquid flow moisture concentration of 0.002 wt%, corresponding to a water removal rate of 99.9%.

Example 5

Using a system having a structure substantially the same as that shown in FIG. 10, a vapor phase feed solution containing 3.3 wt% of water dissolved in ethyl acetate at a pressure of 0.3 bar (gauge pressure) and a temperature of 95 ° C. was used. Feeding was carried out at a rate of 0.14 kg / hr into the tube of the hollow fiber membrane inside the module with an effective membrane area of cm 2. The inner surface of the hollow fiber was coated with the same selective layer as in Example 1.

A nitrogen-containing sweep flow from the gas cylinder at 95 ° C. and 0.3 bar (absolute pressure) is introduced into the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, thereby substantially countercurrent to the flow of the feed liquid. Flow was at 0.6 L (STP) / min. A vacuum pump was used to reduce the pressure of the permeate flow to 0.3 bar (absolute pressure).

Under these operating conditions, the residual liquid flow has a water partial pressure of 0.01524 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00002 bar (absolute pressure), so that the residual liquid flow has a partial pressure inside the sweep flow relative to the moisture partial pressure inside the residual liquid flow. The proportion of water partial pressure was 0.001. This resulted in a residual liquid flow moisture concentration of 0.1 wt%, corresponding to a water removal rate of 89.9%.

Example 6

Using a system having a structure substantially the same as that shown in FIG. 10, a 232 cm 2 vapor phase feed solution containing 12.2 wt% of water dissolved in ethanol at a pressure of 0.2 bar (gauge pressure) and a temperature of 91 ° C. was obtained. The feed rate of 0.07 kg / hr was fed into the tube of the hollow fiber membrane inside the module with an effective membrane area of. The inner surface of the hollow fiber was coated with the same selective layer as in Example 1.

A nitrogen-containing sweep flow from the gas cylinder at 91 ° C. and 0.3 bar (absolute pressure) is introduced into the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, thereby substantially countercurrent to the flow of the feed liquid. Flow was at 0.6 L (STP) / min. A vacuum pump was used to reduce the pressure of the permeate flow to 0.3 bar (absolute pressure).

Under the above operating conditions, the residual liquid flow has a water partial pressure of 0.00460 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00002 bar (absolute pressure), so that the inside of the sweep flow to the water partial pressure inside the residual liquid flow The proportion of water partial pressure of was 0.003. This resulted in a residual liquid flow moisture concentration of 0.2 wt%, corresponding to a water removal rate of 98.7%.

Example 7

Using a system having a structure substantially the same as that shown in FIG. 10, a vapor phase feed solution containing 7.5 wt% of water dissolved in tetrahydrofuran at a pressure of 0.1 bar (gauge pressure) and a temperature of 80 ° C. was used. The feed rate was 1.8 kg / hr into the tube of the hollow fiber membrane inside the module with an effective membrane area of 1.4 m 2. The inner surface of the hollow fiber was coated with the same selective layer as in Example 1.

A nitrogen-containing sweep flow from the gas cylinder at 80 ° C. and 0.3 bar (absolute pressure) is introduced into the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, thereby substantially countercurrent to the flow of the feed liquid. Flow was at 85 L (STP) / min. A vacuum pump was used to reduce the pressure of the permeate flow to 0.3 bar (absolute pressure).

Under the above operating conditions, the residual liquid flow has a water partial pressure of 0.00686 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00002 bar (absolute pressure), so that the residual liquid flow has a partial pressure of water inside the residual flow. The proportion of water partial pressure of was 0.002. This resulted in a residual liquid flow moisture concentration of 0.01 wt%, corresponding to a water removal rate of 99.9%.

Example 8

Example 3 was performed repeatedly except for the following: A vapor phase feed containing 12.7 wt% of moisture at a pressure of 0.1 bar (gauge) was used and the sweep flow was at 95 ° C. and 0.3 bar (absolute pressure). Nitrogen from gas cylinder flowing at 57 L (STP) / min.

Under these operating conditions, the residual liquid flow has a water partial pressure of 0.00047 bar (absolute pressure), while the sweep flow inlet has a moisture partial pressure of 0.00002 bar (absolute pressure), so that the moisture inside the sweep flow to the moisture partial pressure inside the residual liquid flow. The proportion of partial pressure was 0.032. This resulted in a residual liquid flow moisture concentration of 0.014 wt%, corresponding to a water removal rate of 99.9%.

Comparative Example 1

For comparison, the system and module described in Example 8 were operated under countercurrent permeate flow under the same operating conditions but with the sweep flow of nitrogen set to zero so that no nitrogen was introduced as the sweep gas into the membrane module. . Under these conditions, the residual liquid flow had a water concentration of 5.2 wt%, corresponding to only 60% water removal rate.

Example 9

In order to predict the performance of the system using various parameters, the system of the computerized numerical model shown in FIG. 8 was prepared and used. A vapor phase feed solution containing 18 wt% of water dissolved in IPA at a pressure of 0.1 bar (gauge pressure) and a temperature of 95 ° C. was introduced into the tube of the hollow fiber membrane inside the module with an effective membrane area of 2.8 m 2. It was supplied at a rate of kg / hr, the inner surface of the hollow fiber was coated with a selective layer of the same type as used in the above-described embodiment.

A sweep flow of nitrogen at 95 ° C. and essentially atmospheric pressure and having a steam partial pressure of 0.0007 bar (absolute pressure) is introduced into the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, thereby substantially reducing the flow of feed liquid. It was made to flow at 516 L (STP) / min in the countercurrent flow.

Under these conditions, the permeate leaving the module has a calculated water vapor partial pressure of 0.047 bar (absolute pressure). This flow was fed to the compressor to increase the pressure to 6.9 bar (gauge pressure). The resulting high pressure flow was sent to a condenser operating at a temperature of 0 ° C. where the water vapor was condensed. Non-condensable flow out of the condenser was reduced to atmospheric pressure using a throttle valve. The resulting atmospheric flow is estimated to have a partial pressure of water vapor of 0.0005 bar (absolute pressure). The flow was then heated to 95 ° C. and introduced into the module as countercurrent sweep flow.

Under these operating conditions, the residual liquid flow has a calculated water concentration of 0.05 wt%, corresponding to a steam partial pressure of 0.00014 bar (absolute pressure). Thus, the module has a calculated water removal rate of 99.7% and the ratio of the steam partial pressure inside the sweep flow to the steam partial pressure inside the residue flow was calculated to be 0.36.

Example 10

In order to predict the performance of the system using various parameters, the system of the computerized numerical model shown in FIG. 7 was prepared and used. The same feed solution as in Example 9 was fed at the same rate to the same virtual hollow fiber membrane module in the same manner, and using the same sweep flow as Example 9, a calculated water vapor partial pressure of 0.047 bar (absolute pressure) was obtained. And permeate leaving the module. This flow was fed to the compressor to increase the pressure to 6.9 bar (gauge pressure). The resulting high pressure flow was calculated to have a dew point [at 6.9 bar (gauge pressure)] of 74 ° C. This flow was then directed to the membrane gas drying module to reduce the dew point of the gas to 0 ° C. [at 6.9 bar (gauge pressure)]. The pressure of this flow was then reduced to atmospheric pressure using a throttle valve, and supplemental nitrogen from the gas cylinder was mixed with this flow at a flow rate of 103 L (STP) / min. Thereafter, the mixed flow with a calculated water vapor partial pressure of 0.0005 bar (absolute pressure) was heated to 95 ° C. and introduced into the module as a sweep flow.

Under these operating conditions, the residual liquid flow has a calculated water concentration of 0.05 wt%, corresponding to a steam partial pressure of 0.00014 bar (absolute pressure). Thus, the module had a calculated water removal rate of 99.7% and the ratio of the steam partial pressure inside the sweep flow to the steam partial pressure inside the residual liquid flow was 0.36.

Example 11

In order to predict the performance of the system using various parameters, the system of the computerized numerical model shown in FIG. 9 was prepared and used. The same vapor phase feed solution as in Example 9 above was fed in the same manner to the same module using the same sweep flow at the same rate to produce a permeate leaving the module with a calculated water vapor partial pressure of 0.047 bar (absolute pressure). . This flow was fed to the compressor to increase the pressure to 6.9 bar (gauge pressure). The resulting high pressure flow was sent to the desiccant bed to remove moisture at a pressure dew point of 0 ° C. Thereafter, the pressure of nitrogen dried by the desiccant was reduced to atmospheric pressure using a throttle valve. The resulting atmospheric flow has a calculated steam partial pressure of 0.0005 bar (absolute pressure). The flow was then heated to 95 ° C. and introduced into the module as a sweep flow.

Under these operating conditions, the residual liquid flow has a calculated water concentration of 0.05 wt%, corresponding to a steam partial pressure of 0.00014 bar (absolute pressure). Thus, the module had a calculated water removal rate of 99.7% and the ratio of the steam partial pressure inside the sweep flow to the steam partial pressure inside the residual liquid flow was 0.36.

[Examples 12 to 17]

In order to predict the performance of the system using various parameters, the system of the computerized numerical model shown in FIG. 10 was prepared and used. A vapor phase feed solution containing 10 wt% of water dissolved in IPA at a pressure of 0.1 g (gauge) and a pressure of 95 ° C. was fed into the tube of the hollow fiber membrane inside the module with an effective membrane area of 2.8 m 2. The inner surface of the hollow fiber was coated with a selective layer of the same type as used in the above-described embodiment. The flow velocity of this feed liquid flow was changed as shown in Table 1 below and described below.

At a pressure of 95 ° C. and 0.2 bar (absolute pressure), a sweep flow of nitrogen having various water vapor partial pressures shown in Table 1 is introduced into the permeate side of the membrane at an inlet port located near the end of the residual liquid of the module, The flow was allowed to flow at 57 L (STP) / min substantially countercurrent to the flow.

As a result of varying the flow rate of the vapor phase feed as shown in Table 1 below, under certain operating conditions, the residual liquid flow had a water partial pressure of 0.0039 bar (absolute pressure), which was 0.1 wt% of residual liquid flow water concentration. Corresponds to the water removal rate of 99%. The results in Table 1 below show that when the ratio of the partial pressure of water inside the sweep flow to the partial pressure of water in the residual liquid flow is greater than about 0.9, the feed liquid flow rate to the module becomes very low to obtain the desired residual liquid concentration. This results in a high cost and inefficient system. The reason why the feed liquid flow rate to the module is very low in order to obtain the desired residual liquid concentration is that when the ratio is greater than 0.9, the driving force of the partial pressure for the transfer of water vapor over the membrane is also very low. Thus, to obtain a constant residual liquid concentration, the flow rate of the feed liquid to the module must be reduced to allow sufficient time for moisture to be controlled from the feed liquid. The ratio of 0.9 leads to a high cost inefficient system because if the ratio is greater than 0.9, the flow rate of the feed to the module will be lower than if the ratio is less than 0.9. As a result, in order to process a constant volume of feed, a larger membrane area is required, which is less efficient, and the demand for larger membrane surface areas leads to higher membrane costs and ultimately to higher cost systems.

Example Steam partial pressure (bar [absolute pressure]) sweep residue Ratio of sweep to residual liquid partial pressure Feed Fluid Flow Rate (kg / hr) 12 0.0013 0.0039 0.33 6.8 13 0.0021 0.0039 0.55 6.4 14 0.0027 0.0039 0.70 6.0 15 0.0036 0.0039 0.94 5.0 16 0.0038 0.0039 0.97 4.6 17 0.0039 0.0039 1.00 4.2

According to the invention described above, it is possible to selectively remove the first steam at low cost and high efficiency from a feed flow containing a mixture of steam.

The terms and expressions employed in the above specification are terms used for descriptive purposes and are not used in the sense of limitation, and in using such terms and expressions, the features or the features described or described above It is not intended to be equivalent to some of the equivalents, and it is to be understood that the scope of the present invention is limited only by the appended claims and only by this.

Claims (20)

A process for removing a first vapor from a fluid feed stream containing a mixture of vapors, (a) providing a membrane having a feed liquid and a permeate side and selectively permeable to said first vapor, (b) directing the fluid feed liquid flow to the feed liquid side of the membrane to recover the residual liquid flow depleted of the first vapor and recovering the first vapor-rich permeate flow from the permeate side of the membrane; , (c) directing a gaseous fluid sweep flow toward the permeate side of the membrane, causing the sweep flow to flow countercurrent to the flow of the fluid feed stream, wherein the partial pressure of the first vapor inside the sweep flow is Sufficiently low that the ratio of the partial pressure of the first vapor in the sweep flow to the partial pressure of the first vapor in the residual liquid flow is less than 0.9. The method of claim 1, Wherein said gaseous sweep flow is produced by a process selected from membrane separation, adsorption and condensation. The method of claim 1, Said gaseous sweep flow is obtained from a purified gas contained in a vessel. The method of claim 1, Said gaseous sweep flow is obtained by evaporation of liquefied gas. The method of claim 1, (d) directing said first vapor-rich permeate flow to a vapor removal process. The method according to claim 1, 2, 3, 4 or 5, And vacuum is applied downstream of said sweep flow. The method of claim 5, The steam removal process of step (d) is selected from condensation, adsorption and membrane separation. The method of claim 5, The steam removal process of step (d) produces a depleted gaseous flow in which the first vapor is depleted, wherein the concentration of the first vapor in the depleted gaseous flow is sufficiently low, so that the first inside the residual liquid flow. 1 wherein the ratio of the partial pressure of the first steam inside the depleted gas phase flow to the partial pressure of steam is less than 0.9. The method of claim 8, Said depleted gaseous flow is used as a sweep flow in step (c) to recycle said gaseous sweep flow. The method of claim 1, Said membrane is a hollow fiber composite membrane. The method of claim 1, Said first vapor being water vapor. The method of claim 1, Said mixture of steam comprises water vapor and at least one organic vapor. The method of claim 12, Wherein said at least one organic vapor comprises primarily organic compounds having a boiling point greater than 0 ° C. and less than 200 ° C. The method of claim 13, Wherein said at least one organic vapor is selected from the group consisting of isopropyl alcohol, ethanol, ethyl acetate and tetrahydrofuran. The method of claim 1, Wherein the feed liquid flow has a condensation temperature of greater than 40 ° C. at 1 atmosphere. The method of claim 15, Wherein the temperature of the feed liquid flow is maintained at a temperature greater than or equal to the condensation temperature of the feed liquid flow at 1 atmosphere. The method of claim 1, Said feed flow is maintained at a pressure greater than 0 bar (gauge pressure) and less than 10 bar (gauge pressure). The method of claim 17, Said feed flow is maintained at a pressure less than 4 bar (gauge pressure). The method of claim 1, And said ratio of the partial pressure of said first vapor in said sweep flow to the partial pressure of said first vapor in said residual flow is less than 0.5. Removing water vapor from a gaseous feed stream containing a mixture comprising water vapor and organic vapors, wherein the organic vapor mainly comprises an organic compound having a boiling point greater than 0 ° C. and less than 200 ° C., the feed stream flowing at 40 at 1 atmosphere. Having a condensation temperature greater than < RTI ID = 0.0 > C, < / RTI > the feed liquid flow is maintained at a temperature greater than the condensation temperature, and the pressure of the feed liquid flow is greater than 0 bar (gauge pressure) and less than 10 bar (gauge pressure). In (a) a plurality of hollow fiber membranes having feed and residual liquid ends and feed and residual liquid ports and at least two permeate ports, disposed parallel to each other and sealed in a chamber, with optional layers on a support layer; Providing a hollow fiber module comprising a; (b) directing the gaseous feed liquid flow to the feed liquid port of the hollow fiber module, recovering the residual liquid flow depleted of water vapor from the residual liquid port, and water vapor from the permeate port located near the feed liquid end of the module. Recovering the rich permeate flow, (c) directing a gaseous fluid sweep flow to a permeate port located near the residual liquid end of the module, causing the sweep flow to flow countercurrent to the flow of the gaseous feed stream; And the partial pressure of the water vapor is sufficiently low so that the ratio of the partial pressure of the water vapor in the sweep flow to the partial pressure of the water vapor in the residual liquid flow is less than 0.9.